[Elecraft] (KX3) Voltage display (solved)

[Bruce Beford]

Rich, AC7MA explained this quite well on the KX3 Yahoo group just last week:

 

The batteries and external supply are connected at the '+' end. The external
supply '-' is connected to KX3 ground, but not battery '-'. 

With an external supply connected that's higher than the battery voltage,
the battery '-' will be a positive voltage with respect to ground, so
battery voltage is the difference between the measurements of the two
terminals. If no batteries are installed, the battery '-' 

terminal is at ground potential, so the display for PS and BT will be the
same. When the KX3 is running from batteries, the reverse isolation diode
for the batteries puts the battery '-' slightly below ground, which will be
read as 0V, so PS and BT readout will also be the same in that case.

 

73,

Rich AC7MA

 

> Now just the question arises why the BAT display shortly raises to the
> input voltage if you connect the power? ...
 
> Holger, DH3HS